On the ThinkPHP blog today, Stephanie Ehrling has posted about a method for PHP to take in the output of the Nike+ equipment and put it into a usable form.
There is no official API that allows you to use the raw data. Nevertheless the data are sent to the Flash via XML so there is a chance to use them. For PHP Rasmus Lerdorf himself has implemented a class to access these data. The class allows to authenticate a user and fetch the running data of a user in a XML-Format
She gives an example of it in action - simple creation of an object then a call with the username and password. Behind the scenes, the data is pulled in and dropped into a SimpleXML object that includes total distance, total calories burned and data on the most recent run.